Fuel injector

Abstract

 A fuel injector for supplying fuel to an air inlet duct of a spark ignition engine includes a plate valve member (24) which is movable by magnetic forces away from a seating element (23) on a seat member (21) to allow fuel flow through an orifice (22). The fuel flowing from the orifice flows into a bore (42) in a tubular outlet (40) and extending from the bore are at least two diverging bores (43) from which emerge two sprays of fuel. Provision is made to introduce air into the space between the orifice and the entrances to the bores.

Description

[0001] This invention relates to a fuel injector for supplying liquid fuel to an air inlet duct of a spark ignition engine, the injector comprising a valve seat member on one face of which is formed an annular seating element for engagement by a solenoid actuated plate valve member, an orifice in the seat member through which fuel under pressure can flow when the valve member is lifted from the seating element and a tubular outlet through which in use fuel flows from the orifice to the air inlet duct.

[0002] Such injectors are well known in the art and the physical dimensions of the injector have to meet a standard in order to allow interchangeability with injectors which employ different types of valve member. As a result the distance between the orifice and the end of the tubular outlet can be undesirably long when certain spray formations are required. For example, if two sprays are required for use with an engine having two air inlet ducts per cylinder, it is known to form two orifices which are angled to achieve the desired divergence. The extent of divergence is however limited without increasing the diameter of the tubular outlet, by the fact that the spray will impinge upon the wall of the outlet. As an alternative it has been proposed to provide a target at or near the end of the tubular outlet and to direct the fuel as a jet at the target. The target should divide the jet and also break up the jet to form the desired two diverging fuel sprays. In practice however it is found that the sprays are uneven unless the injector is produced to a very high and undesirable, degree of accuracy.

[0003] With other injectors it is desired to produce a single bushy spray that is to say a spray which has a large cone angle. The fact that the orifice is spaced from the end of the tubular outlet limits the degree of spread of the spray and if a conical target is used the same problem is encountered as described above namely that the injector must be produced to a very high degree of accuracy in order to form an even spray.

[0004] The object of the present invention is to provide an injector of the kind specified in a simple and convenient form.

[0005] According to the invention in an injector of the kind specified the orifice is designed to produce a spray within the tubular outlet and at its end remote from the orifice, the outlet defines at least two diverging bores through which the spray passes to form, in the case of an injector having two bores, two diverging sprays.

[0006] Examples of fuel injector in accordance with the invention will now be described with reference to the accompanying drawings in which:-

Figure 1 is a sectional side elevation through the injector,

Figure 2 is a section to an enlarged scale of part of the injector seen in Figure 1,

Figure 3 is an inverted plan view of the part see in Figure 2,

Figures 4 and 5 show alternative shapes for the part.

Figure 6 is a side view of the outer insert member of a two part insert for incorporation in the injector seen in Figure 1,

Figure 7 is a sectional side elevation of the outer insert member seen in Figure 6 taken on the line BB of Figure 10,

Figure 8 is an end view in the direction of the arrow A of Figure 6,

Figures 9 and 10 are opposite end views corresponding to Figures 6 and 7,

Figure 11 is a sectional side elevation of the inner insert member,

Figure 12 is an end view of the inner insert member.

Figure 13 is a sectional side elevation of a modified form of the outer insert member with the section taken on the line YY of Figure 15.

Figures 14 and 15 are opposite end views of the outer insert member of Figure 13,

Figure 16 is a sectional view showing the outer insert members of Figures 13, 14 and 15 with an inner insert member assembled therein, and

Figure 17 is a sectional side elevation of a modified two part insert shown located in an outlet member of the nozzle.

[0007] Referring to Figure 1 of the drawings the injector comprises a hollow generally cylindrical outer body 11 formed from magnetic material and within which there extends a hollow flanged core member 13 formed from magnetic material. Extending within the core is a passage 14 which extends from an inlet 12 in the body.

[0008] Surrounding the core 13 is a former 16 which is formed from synthetic resin material and upon which is wound a solenoid winding 17.

[0009] The body 11 defines an integral radially inwardly extending annular shoulder 18 against which there is trapped by means of a non-magnetic valve seat member 21, an annulus 19. The seat member 21 is held in position by means of a tubular outlet member 15 which in use projects into the air inlet manifold of the engine. The seat member 21 is in the form of a disc the diameter of which is equal to the internal diameter of the body 11 and the disc has a central orifice 22 formed therein. The orifice is surrounded by an inner annular seat element 23 which is engageable by a plate valve member 24 biased by a spring 26 into contact with the seat element and located within the annulus 19. The plate valve member has a plurality of openings 25 and it is formed from magnetic material so that when the winding 17 is energised the flange and core member assume opposite magnetic polarity and the valve member is attracted away from the seating element against the action of the spring. In this situation fuel can flow through the passage 14 and the openings 25 to the central orifice 22. The movement of the valve member towards the shoulder is limited by a non-magnetic shim (not shown).

[0010] Mounted within the outlet member 15 is a non-magnetic tubular outlet 40 having a flange 41 at its end adjacent the seating member, the flange locating in a complementary recess formed in the outlet member 15. The tubular outlet 40 defines a chamber 42 which is closed at its end remote from the seating member except for a pair of divergent bores 43 which extend from the chamber 42. The bores 43 are constructed so that there is defined at the junction thereof a sharp edge 44.

[0011] The orifice 22 can be regarded as being formed in a thin plate and it is designed so that good atomisation of the fuel flowing therethrough is obtained while at the same time it is relatively insensitive to variations in the temperature to which the injector is subjected during use. When in use the valve member is lifted from the seating fuel flows through the orifice to form a spray within the chamber 42 and as the spray progresses along the chamber it becomes evenly distributed and exits through the bores 43 to form two diverging sprays. In a particular application the angle between the two bores 43 is chosen so that the resulting sprays are directed into a pair of air inlet ducts of a cylinder of a spark ignition engine.

[0012] An important aspect of the invention is the provision of flats 45 on the outer side of the tubular outlet 40 as shown in Figure 3. The flats communicate with a transverse recess 46 formed in the end of the flange of the tubular outlet adjacent the seating member. However, the transverse recess may be replaced by rectangular openings such as are illustrated in Figure 13.

[0013] In use when the flow of current in the winding 17 ceases and the valve member returns to the seating element, fuel spray which is already within the chamber 42 continues to move along the chamber and through the bores 43. In so doing air is drawn into the chamber along the flats 45 and the recess 46. In more conventional injectors of this type the fuel spray tends to be halted when the valve member closes onto the seating element and then tends to dribble from the injector outlet thereby resulting in poor combustion of the fuel.

[0014] Figures 4 and 5 show alternative configurations for the chamber 42, the chamber in the example of Figure 4 being tapered towards the bores 43 and that in Figure 5 having a rounded end adjacent the bores 43.

[0015] If it is desired to produce a single bushy spray then three or more bores 43 can be provided the bores being equiangularly disposed about the axis of the tubular outlet 40. It is convenient with this construction to provide the same number of flats 45 as there are bores.

[0016] In a modification (not shown) the flange 41 can be omitted and the tubular outlet 40 secured within the tubular outlet member 15 by reason of its being an interference fit or by means of welding or adhesive. The tubular outlet 40 may be formed from a plastics.

[0017] The tubular outlet 40 and the outlet member 15 could be formed as a single item with the flats 45 defined by axial passages extending the length of the combined unit.

[0018] The tubular outlet 40 can be constructed as a two part insert both parts of which are moulded from synthetic resin material. The insert comprises a hollow outer insert member 47 seen in Figures 6 - 10, which in the example is of triangular section. At its end remote from the seat member 21 the outer insert member has an integral end wall in which there are formed three diverging bores 48 each of which defines an outlet 49. The bores are positioned at the apices of the outer insert member and the side walls of the the outer insert member are formed with rectangular cutouts 50 which extend to a level 51 from the end of the member adjacent the seat member 21. The remaining portions of the insert member are hereinafter termed legs 52 and each leg at its free end is provided on its outer surface, with an axial projection 53 having a rounded outer peripheral surface. The projections locate against a step formed in the bore in the outlet member 15.

[0019] Positioned within the portion of the outer insert member defined by the legs 52 is an inner insert member 54 seen in Figures 11 and 12, which is of tubular form. The end of the inner insert member adjacent the seat member 21 is provided with four outwardly and axially extending projections 55 which when the inner and outer insert members are assembled together locate against the ends of the legs 52. The fact that there are three legs 52 and four projections 55 means that whatever the relative angular position of the insert members there will always be adequate location.

[0020] The other end of the inner insert member is cut off at an angle so as to form a sharp edge which defines a central opening 56. The bore 57 can be tapered as shown in solid outline or it can be substantially uniform in diameter as shown in dotted outline with a tapered section at the end leading to the central opening 56. In the former case a jet of fuel will issue through the opening 56 and three jets of fuel will issue through the openings 49. In the latter case the fuel leaving the opening 56 will be in the form of a spray so that three sprays of fuel will issue through the openings 49.

[0021] The length of the inner insert member is such that the inner end thereof lies below the level 51 but the length of the right cylindrical portion of the outer wall thereof is such that the inner ends of the cutouts 50 form rectangular openings which communicate with channels 58 (Figure 8) defined between the wall of the bore in the outlet member 15 and the flat faces of the outer insert member. The fuel which flows through the opening 56 induces a flow of air along the channels, and through the rectangular openings. The flow of air will entrain any droplets of fuel which may collect on the end of the outer insert member surrounding the openings 49 and on the end of the outlet member 15 which as will be seen in Figure 1, is partly recessed.

[0022] An air flow is also induced through the inner portions of the channels 58 by the flow of fuel through the orifice 22. The air flow taking place through openings to the bore 57 from the channels through openings 59, being defined between the projections 55.

[0023] In an alternative arrangement the openings 59 are omitted by reason of the fact that the projections 53 are flush with the end of the inner insert member. In this case the inner insert member 54 is provided with three drillings (not shown) which extend from the channels 58 respectively into the bore 57, the drillings being angled in the direction of fuel flow.

[0024] Where the insert is designed to produce three sprays of fuel the end portion of the outer insert member can be chamfered, the chamfer breaking into the bores 48, to provide clearance for the sprays.

[0025] It will be understood that the outer insert member may be provided with two bores 48 therefore defining two outlets. In this case two channels only are defined between the bore in the outlet member 15 and the outer insert member.

[0026] Turning now to Figures 13, 14 and 15 there is shown a modification to the outer insert member 47A. In this case the cutouts 50 are eliminated and only the portion of the insert member 47A which in the assembled nozzle is furthest from the seat member 21 is of triangular section the remaining portion of the insert member being of cylindrical section with an annular rim 60.

[0027] Channels corresponding to the channels 58 are defined between the sides of the triangular portion of the outer insert member 47A and the wall of the outlet member 15 and these channels which extend only so far as the cylindrical portion of the insert member, communicate with generally rectangular openings 61 which extend through the side walls of the insert member. The openings 61 are located at substantially the same positions as the inner ends of the cutouts 50 in the example shown in Figure 6 and air can pass through the openings during the use of the nozzle. Figure 16 shows in section, the outer insert member 47A with an inner insert member 54A located in position. The inner insert member 54A corresponds to the inner insert member 54 except that the projections 55 are replaced by a continuous annular rim 62.

[0028] Figure 17 shows a modified form of the two part insert. The outer insert member 63 is secured by adhesive within the outlet member 15 as previously suggested, but in addition, the inner insert member 64 is secured by adhesive or in any other convenient manner, within the outer insert member. Figure 17 shows a two part insert which has two outlets 6 and a pair of flats not shown, are provided on the external surface of the outer insert member 63 to allow air flow into the bore in the inner insert member. Both the insert members 63 and 64 are spaced from the seat member 21 to allow the air flow.

Claims

1. A fuel injector for supplying liquid fuel to an air inlet duct of a spark ignition engine comprising a valve seat member (21) on one face of which is formed an annular seating element (23) for engagement by a solenoid actuated plate valve member (24), an orifice (22) in the seat member through which fuel under pressure can flow when the valve member (24) is lifted from the seating element (23), a tubular outlet (40) through which in use, fuel flows from the orifice (22) to the air inlet duct, characterized in that the orifice (22) is designed to produce a spray within the tubular outlet (40) and at its end remote from the orifice (22) the tubular outlet (40) defines at least two diverging bores (43) through which the spray passes to form in the case of an injector having two bores (43), two diverging sprays.

2. A fuel injector according to Claim 1 characterized by means (45, 46, 58, 50, 61) for admitting air into the tubular outlet (40) at a position removed from said diverging bores (43).

3. A fuel injector according to Claim 2 characterized in that said means (45, 46) comprises flats (45) formed on the exterior surface of the tubular outlet (40) and transverse recesses (46) formed at the end of the tubular outlet (40) adjacent the seat member (21), said recesses (46) communicating with said flats, the tubular outlet (40) being mounted within a tubular outlet member (15), the flats (45) forming with the internal surface of the tubular outlet member (15), channels through which air can flow from the air inlet duct.

4. A fuel injector according to Claim 1 characterized by openings in the tubular outlet (40) and means communicating said openings with the end of the injector which in use is disposed in the air inlet duct.

5. A fuel injector according to Claim 1 characterized in that said tubular outlet (40) is formed by an outer insert member (47, 47A, 63) and an inner insert member (54, 54A, 64) which is located within the outer insert member, said outer insert member defining the diverging bores (48) and the inner insert member defining a bore (57) which receives the fuel spray from the orifice (22) and has an outlet (56) which directs the fuel spray to the entrances of said diverging bores (48).

6. A fuel injector according to Claim 5 characterized in that the wall of said outer insert member (47) is formed with slots (50) extending from the end thereof adjacent the seat member (21) said slots (50) being closed over substantially the whole of their length by the inner insert member (54) so as to form openings through which air can enter into the space defined between the outlet (56) defined by the inner insert member (54) and the entrances to said diverging bores (48).

7. A fuel injector according to Claim 6 characterized in that said inner insert member (54) is provided with channels (59) at its end adjacent the seat member (21) whereby further air can be admitted into the bore (57) in the inner insert member adjacent the orifice (22).

8. A fuel injector according to Claim 7 characterized in that said openings and said channels (59) communicate with channels (58) defined between the outer surface of the outer insert member (47) and the inner surface of a tubular outlet member (15) in which the inner and outer insert members (47, 54) are located.

9. A fuel injector according to Claim 5 characterized in that the outer insert member (47A) defines a plurality of openings (61) in its wall, said openings (61) being positioned to allow a flow of air into the space defined between the outlet (56) defined by the inner insert member (54) and the entrances to said diverging bores (48).

10. A fuel injector according to Claim 5 characterized in that said inner insert member (54, 54A) is provided with a series of projections (55) or a peripheral flange (62) at its end adjacent the seat member (21) said outer insert member (47, 47A) being shaped to locate said projections or flange, and the outer insert member (47, 47A) defining projections (53) or a flange by which it is secured within a tubular outlet member (15).

11. A fuel injector according to Claim 5 characterized in that the inner insert member (64) is secured within the outer insert member (63) and the outer insert member (63) is secured within a tubular outlet member (15).

Drawing